Composite laminates and structures are used in a wide variety of applications, including in the manufacture of aircraft, spacecraft, rotorcraft, watercraft, automobiles, trucks, and other vehicles and structures, due to their high strength-to-weight ratios, corrosion resistance, and other favorable properties. In aircraft manufacturing and assembly, such composite laminates and structures are used in increasing quantities to form the fuselage, wings, tail section, skin panels, and other components.
Aerospace manufacturers increasingly use composite laminates in an effort to reduce the weight and increase the performance of some components. Composite laminates used by the aerospace industry typically comprise a fiber-reinforced composite material. Fiber-reinforced composite materials of this type generally comprise two essential components, namely firstly the fibers and secondly a polymer matrix which surrounds the fibers. The matrix encompasses the fibers and, in the case of thermosetting polymer matrices, is cured and consolidated by a thermal treatment, such that three-dimensional cross-linking takes place. This cure and consolidation has the effect that the fibers are bonded firmly to one another and trapped air and volatiles are removed from the laminate. Similar thermal processing may occur for thermoplastic polymer matrices also resulting in consolidation of the final composite laminate. A range of suitable fiber materials may be used for high performance applications, most commonly carbon fibers but also glass or aramide fibers may be used as well.
A composite component comprising a fibrous material in a matrix material may be produced by arranging one or more ply layers of fibrous material on a forming tool, compacting and then curing the component to form a consolidated component. Conventional compacting methods at certain temperatures (e.g., above 80 degrees F.) for use with composite part layups typically utilize a three-layer system for compacting composite ply layers. In such conventional methods, the first layer may comprise a release film. Release films interact with a top pre-preg surface and must be able to release itself post cure so that little if any of the resin from the pre-preg layup is removed when removing the release film.
The second layer typically comprises a breather material. Such breather materials may be positioned over a surface of a part layup that is subsequently processed under vacuum beneath a sealed vacuum bag. The breather provides a generally uniform breathing path on the surface of the layup that allows air and volatiles to escape from the layup during compaction and curing processing cycles. Removing air and volatiles is desirable in order to reduce part porosity and improve part performance.
The third layer is a vacuum bag for applying pressure to the composite part. Typically, such a vacuum bag comprises a flexible film and is used to enclose the part layup and seal the various component parts of the vacuum bag assembly from outside air. The edges of the vacuum bag are sealed against the edges of the forming tool surface to enclose the part layup against an air-tight mold.
Although most conventional composite compaction systems usually achieve acceptable results, the process of utilizing a combination of a release film, a breather material, and a vacuum bag has certain limitations. For example, the process steps of overlaying the various structures making up the vacuum bag assembly are tedious and labor intensive. In addition, this three level process involves high material costs. Therefore, use of such procedures for such known methods may result in increased manufacturing time, and in turn, increased manufacturing costs. Moreover, use of a three layered system must also be debulked one or more times in order to ensure that the vacuum bag, the release layer and the breather layers all properly conform to oftentimes complex contoured surfaces during composite pre-preg layup and/or compaction. Often, when issues arise from improper debulking, each of the grouping of plies within the part layup may not be properly consolidated, thereby reducing the overall quality of the final cured composite.
There are certain known nylon vacuum bags, such as those provided by Cytec and Airtech under the brand names of Quickdraw and Airdraw, having certain embossed features. However, such embossed nylon vacuum bags have certain limitations when used in systems for compacting composite ply layups. For example, it has been observed that using such embossed nylon vacuum bags tend to remove resin from the composite part layup post cure. Removing resin from the composite part layup can tend to decrease composite performance, such as by adversely affecting the resin-to-ply ratio, oftentimes a critical design parameter of a particular composite laminate.
Accordingly, there is a need for a vacuum bag assembly that may be quickly and easily placed or draped over the entire surface area of a part layup and which conforms to complex part contours during vacuum bag processing. There is also a need for a method of vacuum bagging composite parts that reduces labor costs and material waste, and which avoids or perhaps limits certain costly bagging material costs, such as breather layers and/or vacuum bags. There is also a need for creating a more efficient system for vacuum bagging a composite ply layup, a system that can reduce the amount of touch labor required to prepare a composite ply layup for compaction.